gms | German Medical Science

68th Annual Meeting of the German Society of Neurosurgery (DGNC)
7th Joint Meeting with the British Neurosurgical Society (SBNS)

German Society of Neurosurgery (DGNC)

14 - 17 May 2017, Magdeburg

Preoperative mapping of calculation function by rTMS in patients with parietal brain tumors and correlation with postoperative outcome

Meeting Abstract

  • Sebastian Ille - Neurochirurgische Klinik, Klinikum rechts der Isar, TU München, München, Deutschland
  • Katrin Giglhuber - München, Deutschland
  • Katharina Drummer - München, Deutschland
  • Stefanie Maurer - München, Deutschland
  • Bernhard Meyer - München, Deutschland
  • Sandro M. Krieg - München, Deutschland

Deutsche Gesellschaft für Neurochirurgie. Society of British Neurological Surgeons. 68. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), 7. Joint Meeting mit der Society of British Neurological Surgeons (SBNS). Magdeburg, 14.-17.05.2017. Düsseldorf: German Medical Science GMS Publishing House; 2017. DocDI.17.05

doi: 10.3205/17dgnc276, urn:nbn:de:0183-17dgnc2766

Published: June 9, 2017

© 2017 Ille et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at



Objective: In order to resect brain tumors while preserving the patient’s brain functions, neurosurgeons apply intraoperative direct cortical stimulation (DCS) during awake surgery. Apart from language mapping, some highly specialized centers also map further higher cortical functions such as calculation function. Recently, the feasibility of mapping calculation function by repetitive navigated transcranial magnetic stimulation (rTMS) in healthy volunteers has been shown. The aim of the present study was to correlate the resection of calculation-positive sites in terms of rTMS with functional patient outcome of calculation performance.

Methods: Nine patients with right- or left-sided (7 right-, 2 left-sided) parietal brain tumors (7 gliomas, 2 metastases) underwent preoperative rTMS calculation mapping. We stimulated 52 previously determined cortical sites over the whole tumor hemisphere while patients performed a calculation task with 80 simple arithmetic operations. Pre- and postoperatively, patients performed a standardized number processing and calculation test (NPCT).

Results: The overall error rate (ER = calculation errors per stimulations) for tumor hemispheres was 7.3%. The resection of calculation-positive sites in terms of rTMS worsened the postoperative NPCT result in 6 cases. In 2 cases no calculation-positive sites were resected and the postoperative NPCT result was similar or better than preoperatively. In one case the postoperative NPCT result was better than preoperatively although calculation-positive sites were resected. According to these results sensitivity and negative predictive value are 100%, specificity is 66.7%, and positive predictive value is 85.7%.

Conclusion: The resection of calculation-positive sites in terms of rTMS correlated with postoperative NPCT results in 8 of 9 cases. Despite only presenting a low number of cases, rTMS might be a useful tool for preoperative mapping of calculation function. However, the reliability of the present results has to be evaluated in a larger series.